Radio apparatus



1,620,609 March 1927- SOMERSALO RADI 0 APPARATUS Filed Feb. 9, 1

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Patented Wlar, d, lddla sn res ddt 33 1 GEORGE SOMERSALQ, 01EPROVIDENCE, RHQDE ISLAND.

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Application filed February-9, 1926. Serial No. 869%.-

This invention relates to electrical circuits, particularly of the typein which a threeelement vacuum tube thermionic device may be included,and more particularly to radio 5' circuits of this nature.

One or the objects of this invention is to provide a simple andthoroughly practical form of circuit of the above-mentioned character inwhich certain undesired edects,

to such as, for example, inherent capacities be tween the electrodes ofthe thermionic device, may be not only quickly but also completelyeliminated. Another object is to provide a circuit of theabove-mentioned character which may be rapidly and simply adjusted toachieve the desired action and which may be readily and inexpensivelyincorporated in thoroughly practical :torm. Another object is to providean electrical network of few individual parts or elements and in which abalancing-out of undesired efiects, such as capacity edects, may bequickly and eiiiciently achieved. Another object is to provide a circuitarrangement of the above-mentioned character which is well adapted tomeet the Varied conditions of practical use and which may be easilyembodied in thoroughly commercial form, and particularly adapted for thereception, deac tection or amplification of radio signals. Other objectswill be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, arrangements of parts and in the several stepsand relation and order of each of the same to one or more of the others,all as will be illustratively described herein, and the scope of: theapplication of which will be indicated in the following claims.

in the accompanying drawing, in which are shown several of variouspossible embodiments of the electrical features of my invention,

Figure l is a diagrammatic representation of an alternating currentnetwork embodying certain features of my invention, and

Figure 2 is a like diagrammatic representation oi the system or networkoi": Figure 1 but as embodying a three-element thermionic device orvacuum tube.

Figure 3 is illustrative of a modified form of the circuit arrangementof Figure l, and

Figure 4 is illustrative diagrammatically of the arrangement of Figure 3but having embodied therein a three-element vacuum tube or so-calledaudion. Similar reference characters refer to similar parts throughoutthe several views in the drawing. co As conducive to a clearerunderstanding of certain features of this invention, it may i at thispoint be noted that in many circuits having embodied therein athree-element thermionic device, such as the so-called c5 audion, thedesired action of the circuit is oftentimes but inappreciably attainedby reason of the undesired or detrimental eflects on the circuit and itsaction due to such factors, for example, as the inherent eapac- 70 ityor capacities between the electrodes of the device and which act asunintended coufilings between difi'erent parts of the circuit. llanyattempts have been made to devise circuits or methods whereby suchdetri- 75- mental efiects may be avoided, but such attempts have beencharacterized by the achievement of their corresponding objectsto only amoderate extent. Particularly has this been true in circuits devisedto.neutralize so inherent capacity between electrodes of the vacuumtube, as the latter is used in the translation or am lification and thelike of radio si nals. Eiilch prior attempts are further 0 aracterizedby the vital deficiency 85 that they do not achieve or even approachcomplete neutralization, since they proceed upon the erroneousassumption that, in prac tice, unity coupling maybe achieved between twocoupling coils inductively related to one to the other. Such priorattempts, therefore, achieve neutralization of these undesired ede'ctsto no greater extent than it is possible in practice to achieve unitycoupling. Une of the dominant aims of this an invention is to provide acircuit arrangement and a method whereby such. deficiencies as thosepointed out above may be avoided, and complete neutralization achievedin a thoroughly practical and simple manner.

Referring now to the drawing and more particularly to Figure 1, there isshown diagrammatically a circuit arrangement in which the severalpartsthereof may be so balanced that the edect of one element in rot thecircuit upon anotherelement or part oi the circuit may be completelyeliminated. This network of Figure 1 1s arranged to constitute a bridge,and, for purposes of illus Mill tration, the bridge circuit 4 includesthe Rio following elements arranged in the following manner:In Figure 1,0,, and 0,, represent two capacities or condensers arranged in seriesand bridged across the points G and Q which points are in effect theterminals of an inductance B. Bridged across .the inductance B and henceacross the points G and Q is a current indicating device A. Connected topoint Q is one end of an inductance B this inductance B is inductivelyrelated to the inductance B and as indicated in Figure 1, the twoinductances, when placed end to end as shown in Figure 1, will be seento be wound oppositely. The other terminal of the inductance B indicatedby the points F, is connected to a point P intermediate of thecondensers 0,, and o but through a device adapted to produce anelectro-motive force, such as the secondary winding of a transformer E.

With such a circuit arrangement or network of elementsas is abovedescribed in connection with Figure 1, the current indicator A, when thedevice such as the transformer winding E is operative, will indicatezero currentwhen the following relation has been established where L isthe self-inductance of the coil -B and where M is the mutual inductancebetween the coils Band B,. This relation will be seen to include factorswhich are in practice actually capable of realization. In other words,the self-inductance of the coil B is a definite calculatable factor andthe capacities of the two condensers are likewise definte factors. Themutual inductance M is not a factor that is' based on the erroneousassumption that unity coupling is achievable in practice, but is onethat may be directly realized. Hence, by making the coupling between thecoils .B and B variable, assuming all the other factors above set forthin this relation to be fixed, the

factor M may be adjusted to a value to establish the above-mentionedrelation and hence to establish a complete balance in the electricalnetwork.

Or, on the other hand, assuming that the elements of the vacuum tubewill be seen to correspond to the points P, F and G of Figure 1. Theinductance B of Figure 1 will be seen to be, in Figure 2, part of theinput circuit of the vacuum tube and across the, inductance B isconnected a variable condenser C, to indicate that the input circuit ofthe network embodying my inven tion may be a tuned circuit. Theinductance B of Figure 1 will be seen in Figure 2 to be connectedbetween the filament F and the point Q forming one terminal of theinductance B; the two inductances B and B, of Figure 2 are shown in thelatter figure inductively related to each other but placed end to endsubstantially, and hence, to achieve the same electrical action as theydo in Figure 1, the windings of one inductance, in Figure 2, are shownas coiled or wound oppositely from those of the other inductance. Theinductive relation of these two coils B and B is preferably variable.

- The capacity o of Figure 1 will be seen in Figure 2 to be interposedbetween the point or plate P and the point Q, just as in Figure 1, whilethe capacity 0,, of Figure l is shown in Figure 2 as being the inherentcapacity between the plate P and the grid G of the audion. Between thepoint or plate P of Figure 2 (intermediate of the condensers 0,, and oas is also the case in Figure l) and the point F, the filament in Figure2, is interposed a source of direct current electromotive force,indicated by the battery E and to further illustrate the em bodiment ofmy invention in a circuit well adapted for radio communication purposes,I have shown in the plate circuit also a coil B this latter coil may bethe primary winding of a coupling transformer, the secondary of whichforms part of the input circuit to a subsequent vacuum tube or it maybe, for example, any suitable form of translating device. The coil orinduc-' tance B, of Figure 2, may be associated with a suitable channel1 of communication, such as an antenna circuit, for example, and theassociation may be made in any suitable manner, such as by a conductiveor induct ve coupling, for example. The capacity o is shown inFigure 2as variable.

To neutralize completely the effect of the inherent capacity 0,, betweenthe plate P and the grid G, which capacity acts as a coupling orfeed-back between the output or plate circuit of the audion to the inputor grid circuit and thus acts to cause the system to oscillateundesirably and with detrimental effects, such a relation, with thearangement or network of Figure 2, is established that an alternatingelectromotive force' between the plate P and the filament F can have noeffect whatever upon the input circuit; such a condition wouldcorrespond with an adjustment of the parts such that, in Figure 1, therewould be zero indication of current Hill reaaeoe flow in the indicatingdevice A. The device A of Figure l finds, in a sense, its counterpart inthe network of Figure 2 in the condenser C. Accordingly, the couplingbetween the coils B and B is so adjusted that the relation hereinaboveset forth is established, or this relation may be achieved by anadjustment of the variable condenser 0,, or by making both of theseadjustments. In either of these instances, and as long as theabove-mentioned relation is established, the network or system of Figure2 becomes balanced and neutralization of the inherent capacity betweenthe grid and the plate is completely and absolutely achieved, asdistinguished from neutralization to an extent only commensurate withthat to which unity coupling may be achieved in practice as ischaracteristic of prior attempts to eliminate the retroactive effect dueto the inherent capacities between the electrodes of the vacuum tube.

In Figure 3 of the drawing 1 have shown a modified form of network andthis balancing network of Figure 3 will be seen to be substantiallyidentical in action with that of Figure l excepting that one terminal ofinductance B is connected to the inductance B at the point Gr, insteadof point Q as in Figure l. The coils B and B of Figure 3 are otherwise,as to relation inductively and as to directions of winding, the same asin Figure 1. The relation of balancing, pointed out above in connectionparticularly with respect to Figure 1 and also in connection with Figure2, holds true for the balancing network of Figure 3, and in derivingfrom the network of Figure 3 a network in which is included athree-element vacuum tube (similarly as the balancing network of Figure2 is derived from the balancing network of Figure 1), there results acircuit arrangement shown in Figure 4. This balancing network of Figure4 will be seen to be distinguished from the network of Figure 2 by theconnection of one terminal of coil B to the coil B, not at point Q, asin Figure 2, but at the point or terminal Gr, just as is the distinctionbetween the networks of Figures 3 and 1.

The condition for balancing, in the network of Figure 4, and to achievecomplete neutralization of the effect of the inherent capacity betweencertain of the electrodes of the vacuum tube remains, however, the sameas that relation which must be established to achieve balance in theelementary circuits of Figures 3 and 1.

it will thus be seen that neutralization of inherent capacity effects inthe three element thermionic device may thus be achieved as such, andnot inerely in part or to an extent, as has been characteristic of priorattempts, commensurate with that to which unity coupling may be arrivedat in practice. In accordance with my invention, therefore, undesiredand detrimental effects and actions in the circuit of a vacuum tube maybe completely eliminated and prevented, since their elimination is madedependent "e upon such electrical factors as may be actually and totallyrealized in practical circuits of this nature. The achievement of trueneutralization, as I am able to do byreason of my invention, results inmany '75 thoroughly practical advantages; among the latter may be notedthe tact that greater scnsiliveness of the apparatus is brought about,the apparatus, when used for the reception. of radio signals, isinherently made capable of handling, at the input, far greater amountsof initial energy, and even though much greater amounts of energy maythus be initially utilized, the adjustment, manipulation or handling ofthe apparatus is not in any way impaired or made additionallcomplicated. It is a known fact that, wit receiving systems orapparatuses embodying arrangements corresponding to prior art-- temptsto achieve neutralization, the turns included in the primary coils oftransformers'which couple one stage of amplification to another have tobe maintained ata numher very low; this results in the transfer of verysmall amounts of energy from one stage to a subsequent stageotiamplification, with the result that the apparatus is operated at notonly a very small proportion of the load which it could carry but alsoat very low eficiency. Any increase in the number of turns thus employedwith corres onding increase in the amount of energy andled causes suchapparatuses to become promptly inoperative in so far as neutralizationis concerned; they are thus rapidly brought into a condition ofoscillation or squeeling, with its well-known detects.

By reason of my invention, however, the achievement of neutralizationimposes no limits upon the amounts of energy handled 11119 ortransferred from one stage of amplification to the other, and thuscomplete utilization of the'tull capacity of the vacuum tube or tube andits circuit to handle a load may be achieved, and this without danger ofEEG bringing about feed-back action and resultant oscillation orsqueeling. Thus, also, no restrictive limitations as to amplificationare imposed upon the system or apparatus. Furthermore, it will be seenthat the tee apparatus or circuit arrangement is simple, may be readilyand conveniently manipulated or adjusted, and may be readilyincorporated in commercial form.

As many possible embodiments may be made of the mechanical features ofthe above invention and as the art herein described might be varied invarious parts all without departing from the scope of the invention, itis to be understood that all matter hereinabove set forth or shown inthe accompanying drawings is to be interpreted as illustrative and notin a limiting sense.

I'claim as my invention:

1. In a signaling system, the combination of a three-element thermionicdevice with an input circuit and an output circuit, said in-.

put circuit including a coil, one terminal of which is connected to thegrid of said device and said output circuit connecting the plate andfilament of said device; and means for preventing feedback of energyfrom the output circuit to the input circuit through the inherentcapacity between electrodes of the device, said means including acapacity interposed between the other terminal of said coil and theplate of said device, and a separate coil electrically interposedbetween one terminal of said first-mentioned coil and the filament ofsaid device, said coils being inductively related to each other and theone wound oppositely with respect to the input circuit through theinherent capacity between the grid and plate electrodes of said device,said means including a capacity interposed between one terminal of saidinput coil and the plate, the other terminal of said coil beingconnected to the grid, and a second coil wound oppositely with respectto said input coil and interposed between one terminal of the said inputcoil and the filament of said device, and inductively coupled to saidinput coil, the inductive coupling between said two coils being lessthan unity, and means for predetermining at will the relation betweensaid coupling and said capacity so that the terminals of said input coilare at substantially the same potential.

3. In a signaling system, the combination of a three-element thermionicdevice with an input circuit and an output circuit, said input circuitincluding a coil, one terminal of which is connected to the grid of saiddevice and said output circuit connecting the plate and the filament ofsaid device; and means for preventing feed-back of energy from theoutput circuit to the input circuit through the inherent capacitybetween electrodes of the device, said means including a condenserinterposed between the other terminal of said coil and the late of saiddevice, and a separate coil e ectrically interposed between one terminalof said first-mentioned coil and the filament of said device, said twocoils being inductively related to each other and the one woundoppositely with respect to the other and means for changing at will thecoupling between said two coils, said coupling being less than unity.

4.-. In a signaling system, the combination of a thermionic amplifyingdevice having plate, grid, and fil'ament electrodes, with an lnputcircuit and an output circuit, said input circuit including a coilconnected between the rid and plate electrodes of said device, and saidoutput circuit connecting the plate and the filament of said device,whereby, when an alternating electromotive force is impressed on theinput circuit, said electromotive force is amplified and said outputcircuit responds thereto; and means for preventing the amplifiedelectromotive force in the output circuit from reacting upon the inputcircuit through the inherent capacity between plate and grid electrodesof said device, said means including a condenser arranged to-form withthe input coil a series connection between the grid and plate,electrodes, a coil wound oppositely with respect to said/input coil andinductively related thereto and interposed between one terminal of theinput coil and the filament of said device, and means for relating themutual inductance of said two coils to the capacit of said condenser sothat the terminals 0 said first-mentioned coil will be at substantiallythe same potential.

5. In a signaling system, the combination of which is in electricalconnection with the grid of said device, and said output circuitconnecting the plate and the filament of said device whereby, when analternating elebtromotive force is impressed on the input circuit, saidelectromotive force is amplified and said output circuit respondsthereto; and means for preventing the electromotive force in the outputcircuit from affecting the in ut circuit through the inherent capacitybetween the plate and grid electrodes of said device, said meansincluding a condenser interposed between the other terminal of saidinput coil and the plate of said device and a separate coil woundreversed with respect to said input coil and inductively relatedthereto, the coupling therebetween being less than unity, said separatecoil being interposed between one terminal of the input coil and thefilament of said device; and means for establishing such a relationbetween the said. coupling and the capacity of said condenser that theterminals of said input coil will be at substantially the ea scainputcircuit including a coil B connected between the grid and plateelectrodes of said device, and said output circuit connecting the plateand the filament electrodes of said device, whereby, when an alternatingelectromotive force is impressed on the input circuit, saidelectromotive force is amplified and said output circuit respondsthereto; and means for preventing the amplified electromotive force inthe output circuit from reacting upon the input circuit through theinherent capacity 0 between plate and grid electrodes of said device,said means including a condenser arranged to form with the input coil Ba series connection between the grid and plate elec trodes,.and a coil Bwound oppositely with respect to said input coil B and inductivelyrelated thereto and interposed between one terminal of the input coil Band the filanlent electrode of said device, the mutual inductance Mbetween the coils B and B being related to the self inductance L, of thecoil B so that where 0,; is the capacity of said condenser.

input circuit and an output circuit, said input circuit including acoil, one terminal of which is connected to the grid of said device, andsaid output circuit connecting the plate and the filament of said devicewhereby,'when an alternating electromot-ive force is impressed on theinput circuit, said electromotive force is amplified and said outputcircuit responds thereto; and means for preventing the electromotiveforce in the. output circuit from affecting the input circuit throughthe inherent capacity between the plate and grid electrodes of saiddevice, said means includinga condenser interposed between the otherterminal of said input coil and the plate of said device and a separatecoil wound reversed with respect to said input coil andinductivelyrelated thereto, the coupling therebetween being less thanunity, said separate coil beinginterposed between said other terminal ofthe input coil and the filament of said device; and means forestablishing such a relation of coupling that the terminals of saidinput coil will be at substantially the same potential.

In testimony whereof, I have signed my name to this specification this8th day of February, 1926.

' GEORGE SOMERSALO.

